Your problem will occur only if the kepub books you buy and load on your device after purchasing it come from the WHSmith proprietary store. The Touch can sync with only one store. So, if from the get-go, you buy from the Brit version of kobobooks.com, and later purchase from the Canadian version of kobobooks.com, you should be fine. You can use Adobe ePUBs from anywhere, without any problem, as long as you use the same ADE account.

If you know for sure you are moving to Canada, I would create a kobo account and put honest and accurate information in when you do it. When you move, change the details so that your Canadian address and credit card are now the identifiers for your Kobo account. As an alternative, I suppose you can go Canadian from the get go, and always shop the Canadian store.